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No Model.) 2 snetssjne'en 1 A, BVRARD. HARDENING AND TEMPBRING ARMOR PLATES, am. No. 387,712. pgaaerltew Aug. 14, 1888.

l i i FAG@- 4 "2 lSheets-'Sheet 2.

(No' Model.)

A. EVRARD.

' limmnznllm` AND TBMPERING ARMOR PLATES, aw.

Patented Aug. 14, 1888.

1 To alia/72.401111, it may concern:

' l vented certain new and useful Improvements IOv o tempering of armor-plates and other pieces of ALFRED EVB/ARD, OF PAR IS, FRANCE, ASSIGNOR TO THE COMPAGNIE lANONYlllE DES FORGES DE CHATILLON ETuOOlillllENTRY.

ltARCiEhllblG AN TNiP-ER lne ARMOR-PLATES, sie

SPECETICATIN--formng part of LettersPatent No. 387,712, dated August le, 18de.

Application tiled September l, 1856. Serial No. 913,899.

(No specimens.) Patentedl in France June 30, 1886, No. 11'Li2;

in England A ngnst 24, 1886, No. 10,823. and in Italy September 18, 1886, XL, 350.

B e' itknownthat l, ALFRED Eva-inn, of Paris, 1n the Republic .ot France, have inin Hardening or Temperiug Armor-Plates, *Qa'nnon-lubea and other Large Objects of that Order, (for which improvements Letters Patent have been granted in Great Britain, Nov.10,823, dated August 24, 1886; in France, No:ll7,1l2, dated June 30, 1886, and a certica'te of addition thereto, dated July 20, 1886,A and inlItaly, Vol. 40, No. 350, dated A eptember 18, 1886,) of'whieh the following specification is a full, clear, and exact dcscription.,

The invention relates to the hardening or armor for. ships or fortifications of all kinds, cannon-tubes, breech-pieces, hoops, projectiles, cylinders for rolling, axles, rings, iron plates, and other large objects of that order.

In tempering, as is Well known, the etl'eet of plunging the het metallic object to hetero` pered into the comparatively cold temperingbath is, ii rst, to reduce with more or less suddenness the temperature of the outside, which in turn abstracts the heat from the inner portions; and the tendency of this successi ve cooling is to cause u ncqnal contractions in the mass, which pnt it under stress or strains that areapt to weaken the strength ofthe object, to warp it, and to cause'rupturcs therein. l't is also knownthat the effect of tempering is, or has been, different in the case of' large objects from what it is when applied to small ohiccts, fornot only Vis there greater liability to the production of injurious or destructive strains and ruptures,l owing to the greater inequality in the contraction of dil't'erent portions ofthe mass, but it is also the fact that ,the tempering action in smallobj ects pervades the mass, while in large objects it is, or has heretofore been, confined', comparatively speaking, to the surface.

I am aware that heretofore the tempering of armor-plates, cannon-tubes, and other objects of that order has been eftfected in oil; but this process is thought to be oiijeetionable'for several reasons. lt is not only liable to warp the steel, but sometimes causes the surface te 5ecrack, and, since the oil is not a goed conductor of heat, there may arise differences et" temperature in dili'erent parts of the bath, which would cause unequal tempering and increase the dangers from unequal contract-ion.

- sudden lowering of temperature than the in-v` ner parts, for the object almost instantiy decoin poses the oilsin contact therewith, whereas the inner parts must await the slow action of 7o conduction. It has also been proposed to temper armor-plates in water; but this process has not been employed to the extent ol" the oil-tempering, if at all. The difficulties before mentioned, or sonic et them, are or would be encountered in even greater degree.

I have discovered that armor-plates, cannon-tubes, and other large objects of that order can be tempered 'in molten-metal baths with great advantage over the use of oil or 8o other non-metallic baths, and 1 have alsodctermned how such tempering can usefully be carried on. The molten metal, being'of goed conductivity, maintains an equality of temperature in all parts of the bath, anchas it may S5 be raised to a very high temperature, thesnrfaces and angles can be maintained to the end: ot' the tempering operation at such a high ternperature that the object, evenwhen .of very hard steel,will support without danger thev 9o y strains and stresses whichthe' tempering develops. Moreover, the moltenmctal, not bci'ng decomposed or va orized at the temperatures to which it is exposed, abstracts the heat from the surface in a more vgradual and unig5 forni imanncr and more nearly analogous to the abstraction of the heat from the interior of the object, for when the hot armor-plate,

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cannon "nube, 30x' uiiii'fi oiiieaigai; 0i ilnib oi'illni' in iinmei'sei'l, .iii iin: imillnn-meliil 'with lliiimili- Sii'lc pziiiiiiclus of Sincli object pin't iilli timii' lientliy confliin'ft'ini'i in iin? iidjin'cnb pi'irtiirl ,'i-z 5 of the mollen metil ind 'mine ilmii' i-iiniiini'iiture to :i degree iflepiincling upon lli@ I'Qlziiiii'i; specific lieiiis inni Siiiiiliii' ciiinlil,inxi5,:iiid ii suliieiently ".ipii'l jii i'ognliu' anni 0mm iniiiifchange of lient; iiy confliiciinu tlinn inline pini-n i from tliu intni'ioi' 0i' ilin ohja-cl. lin iin', iiiiliiiiln ilieifiof, fram -lllc oiilf-:iiiiiol' ille @lijn-ifi". in ille molten meal in miiiii'li liliei'nwiiii, iinil l'i'fnn this inollifzn melnl in iiiiionlci' pfii'lfol1 lic liiitlnwlieieiii when ii @smil-iii' olijf'ci; iii immersd in oil i'u' minimi i'iiisn the lieiiipiii'iilin'n above :i ci'linin poini., tlm oil in minimi willi the object i0 lic tinjiii'eil il; ilecmiiiinsrui'i., :inil i thus nearly inst-.iniinnioi'isly reduces lili@ twin @liu 3 um@ nilliiilii, iin: ni'iniil in lin', liii'inifi' furie, lining; ilii` 'limi inigiiii'iiing of ii mi from kl. i0 tlw mi'zl'iii imiiii um l iiiiin is cslriiiliiliecl, iii iiii'i 'fiiliiiiinili'ljyf williin wiile nl iimwin iwi izililii nl inliipli'il inn :mil iiegnli l: n, rind i Minimi ng fiction living" iliin i@ `fi @niiipai'iil,i.w ly prolonged cnndni, iin n? heul, Wlimoiin ii'i tlm inili' @una (if. i1., willi oil-bzitliii) the teniftiigi'ing limit is lifi'i by'ihe deci'iinposiiig lenigieiiii imi nl' flli@ oilis, :inil llici tempefiing' in Qlllctiiil iii :i very i'iimiilvi'nlile 40 extent, if not niziiniy, iq.' :in ilinii'iuiiion nl' limi', dni: iO the coiivisimi iii' liquid. intl) gii iii mi por' :mil not simply' ln ifcimlnclicni.

ln iieinp'i'iiig; Simili fili'iffcls in iiniillcii-iiiiiiil li: Lim, :i5: inn.: liiii'igifiliin liwn elim-ivd, llic nininni :iclviiin 0l illu lizii'n :mil iilnx nl ijfecli wi lin lnipei'eil :mi also @Moni iziliy ilill'i'i'nni l'i'i'iln ille;

3U lil@ il Y mit" llllij liniilr:

iililiizcii lo im iviniwi'vil, imi nlm li) lin' ifinzii` Sri IOC

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sorted through the projecting lower end of the rod. The chamber R permits this to be done. 'lhe tube is then lifted, and another key is inserted in the rod above the tube. WVlicn the tube is out of the former, it is transported above the vessel B, in Whichtheiead bath has been raised to the desired temperature. The dragchain J' is then fastened to the end ol" the rod V and the tube drawn into the bath, in which it is allowed to remain for 'the time judged necessary.

The precise means described, it will be observed, are not of the essence oi' the invention. "lhc means forheating and for effecting the im mcrsion can be varied according to the form of thc pieces. liloreover, it is not designed to claim herein nor to restrict thc claims to the precise means of handling the pieces to bc tf'finpered.

l claim as my invention or discoveryl. The improvement in tempering or hardcning armorplates, cannon-tubes, and other large objects of that order, consisting in heating the object to or about a cherry-red or or angeyellow, forcing it while thus hot undera tempering-bath of molten metal having an ini tial temperature of about H10()n ceutigradc, and beingof a volume readily comparable with that of the object to bc tempered, particularly n bath of molten lead of threefor four times the weight vof said object, and keeping the said object submerged till it has attained the temperature of the molten-metal bath, so that the tempering or hardening is effected by a com inn'atively prolonged conduction from the surface of the armor-plate, cannon-tube, or other large object of that order to the molten metal in contact therewith, and also through the mass of the said object and of the molten metal, under a surface-pressure in excess of that attained by the old use of non-metallic liquids, substantially as described, thespeciiied conditions of temperature andthe like being variable more or less, according to the nature of the metal to be tempered, the degree of temper to be produced, and the special circumstances, as the skilled operator may determine, s hereinbefore set forth.

2. The new and improved apparatus for tempering or hardening armorplates, cauuon tubes, and other large objects of that order in molten-metal baths, consistingof two furnaces, cach provided with means for heating the contcnttand one of them containing a moltenmetal tcmpcringbatlnand being also provided with means for forcing the large objects to be tempered under the molten metal of the bath and holding them there, and, in connection with said furnaces, ol mechanical appliancessuch as trucks and lifts-#for transferring said large oigjects to the furnace containing the metal bath from the other o' said furnaces, sub stautiall y as described. n

In testimony whereof I have signed this specificati on in the presence of two subscribing witnesses.

ALFRED EVRARD. "Witnesses J. JANTET, t J. A. CoUnNran BiLLro. 

